clc;
syms x y;
f=(x^2-2*x)*exp(-x^2-y^2-x*y);
F=taylor(f,[x,y],[0,0],'Order',8);
collect(F,x)%泰勒级数在x=1，y=a处展开

syms a;
F=taylor(f,[x,y],[1,a],'Order',3);
F1(x)=simplify(F)